Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$69.26	13.173%	$78.3836	$78.38	$78.40	$78.40
Purchase #2	$29.37	9.123%	$32.0494	$32.05	$32.05	$32.00
Purchase #3	$67.43	8.637%	$73.2539	$73.25	$73.25	$73.30
Purchase #4	$16.90	8.736%	$18.3764	$18.38	$18.40	$18.40
Purchase #5	$186.64	4.172%	$194.4266	$194.43	$194.45	$194.40
Purchase #6	$40.96	13.351%	$46.4286	$46.43	$46.45	$46.40
Purchase #7	$42.27	9.655%	$46.3512	$46.35	$46.35	$46.40
7 purchase totals =	$452.83		$489.2697	$489.27	$489.35	$489.30